The Texan Confederate army under General Henry H. Sibley, their supply train destroyed by the 1st Colorado Union Volunteers at Glorieta Pass, have only one prize remaining: a battery of Union artillery captured at the Battle of Valverde. The Texans, their force decimated, dispirited by the absence of fallen comrades, are determined to have some glory to show for their terrible losses. But standing in their way are Union Captain Alastar O'Brien and the Colorado Volunteers.

Young quartermaster Jamie Russell, wounded and taken prisoner by Union forces, devises a way to bring the guns to Texas. He escapes, convinces Sibley's brain trust to try his desperate scheme, and his plan becomes grim reality as both the Blue and the Gray are inexorably drawn into the deadly drama that is the Civil War.